1. Field of the Invention
The present invention relates to a pixel interpolation device for pixel interpolation in enlarging or reducing image data and a camera, such as a digital still camera, a digital video camera, or the like, which has the pixel interpolation device built in to provide a pixel interpolation function used in digitally enlarging or reducing a captured image.
2. Description of the Related Art
In general, cameras, such as digital still cameras, digital video cameras, etc., have a digital zoom function built in, which is adapted to enlarge or reduce an image without using optical operations/functions. Such cameras responds to a zoom operation by the user to enlarge or reduce (zoom in or out) an image by creating (interpolating) pixel data of the enlarged or reduced image on the basis of pixel data from the original image. At this point, the pixel data is created by performing operations on multiple pieces of existing pixel data and interpolation coefficients selected according to the interpolation position.
For example, an image enlarging device has been proposed in Japanese Unexamined Patent Publication No. 5-7584. According to this device, data from at least four neighbor pixels arranged in one of the horizontal and vertical directions are each multiplied by a given coefficient. The resulting products are then added together to thereby produce pixel data to be inserted between the two central ones of the four pixels. Further, at least four pieces of pixel data previously created and arranged in the other of the horizontal and vertical directions are each multiplied by a given coefficient. The resulting products are then added together to thereby create pixel data to be inserted between the central two pieces of pixel data.
Also, an imaging device has been proposed in Japanese Unexamined Patent Publication No. 10-63828, which enlarges an image formed by an array of pixels each containing digital data by interpolating between adjacent pixels in the image. This device includes a memory in the form of a lookup table which is stored with filter coefficients representing a spline weighting function and an operation circuit adapted to use the coefficients to calculate pixel values to be interpolated in the enlarged image.
Thus, the conventional image enlarging devices perform operations using coefficients on pixel data but merely use a table stored with general-purpose coefficient data and an operations circuit which do not take the features of coefficients in enlargement interpolation into consideration. Therefore, the table (memory) and the operation circuits have to become redundant in circuit arrangement, which may result an increase in circuit scale.